1. Field of the Invention
This invention relates in general to solid fuel combustion apparatuses, and more particularly, to lime kilns at pulp and paper mills.
2. Description of Related Art
In U.S. Pat. No. 4,412,814, issued to Dennis et al. on Nov. 1, 1983, there is disclosed a dual purpose gas and solid fuel burner for a brick kiln. With reference to FIGS. 8, 11 and 12, the burner includes a sawdust conveying conduit (32f) with attached adapter (i), which is open to the atmosphere, an air conduit (32e) and a pipe fitting (32d) conjoining the sawdust conveying conduit and air conduit. An airstream is introduced into the air conduit (32e) and through the burner unit producing an aspirating effect in the pipe fitting (32d) which causes an airstream to flow into the respective adapter (i). The airstream entering the adapter (i) flows along the sawdust conveying conduit (32f) and thereby induces the flow of sawdust through the burner unit.
In U.S. Pat. No. 4,313,386, issued to Boldt et al. on Feb. 2, 1982, there is disclosed a system for transport of solid particulate fuel and air to the burner ejector of a kiln. The fuel particles are delivered by an adjustable fuel feeding arrangement (16) to a venturi ejector (18), which produces a negative pressure in the fuel feeding arrangement to suck the fuel particles into the venturi, and delivers them, along with air, through a supply conduit (20) to a rotary distributor (22).
In U.S. Pat. No. 4,085,976, issued to Edwards et al. on Apr. 25, 1978, there is disclosed a pulverulent material metering and delivery system. Pressurized air is provided from the header (46) to the valve (48), the conduit (50) and the hose (44) and then to the venturi nozzle (42) from which it is ejected into the lance member (52). Operation of the nozzle (42) creates a lowered pressure in the venturi housing (40) which draws air through the valves (28,30), the metering conduit (16) and the hose (36) into the housing (40). The air induced through the feed air opening (18) onto the surface of repose (17) of the coal engages the coal particles and entrains them in the air stream at the left end of the metering conduit (16).
None of the aforementioned solid fuel burner apparatuses aspirate solid fuel from a low pressure region within a kiln. Instead, the previous solid fuel burner apparatuses aspirate solid fuel from a location external to the kiln, and then, subsequently to aspirating the solid fuel, entrain the solid fuel with a moving stream of fluid into the kiln.
Additionally, none of the above solid fuel combustion apparatuses preheat the solid fuel before it is ignited within the kiln. This limits the maximum temperature the kiln can reach.